The present invention relates to a fluorine laser device, and particularly relates to a fluorine laser device in which a band of a wavelength is narrowed by a dispersion prism.
Band narrowing means for narrowing a band of a wavelength of laser light with use of a dispersion prism is conventionally known, and is shown, for example, in the reference, Canadian Journal of Physics, Vol. 63, PP. 214-219, 1985. FIG. 21 shows a fluorine laser device in which the band of a wavelength is narrowed by using the band narrowing means which is disclosed in the aforementioned reference, and the prior art will be explained below based on FIG. 21.
In FIG. 21, a fluorine laser device 1 includes a laser chamber 2 containing laser gas being a laser medium. High voltage is applied across discharge electrodes not illustrated which are placed inside the laser chamber 2 from a high-voltage power supply not illustrated, and discharge occurs across the discharge electrodes, thereby generating laser light 11.
At both end portions of the laser chamber 2, fixed are a front window 107 and a rear window 109 for transmitting the laser light 11. In front of (right side of FIG. 1) and behind the laser chamber 2, respectively placed are a front slit 116 and a rear slit 117 having a front opening 33 and a rear opening 34 each having a predetermined width.
In front of the front slit 116, placed is a front mirror 8 for transmitting part of the laser light 11 at a predetermined transmissivity to emit it. Further, behind the rear slit 117, disposed are two dispersion prisms 118 and 118, and a rear mirror 106 for totally reflecting the laser light 11 is disposed behind the prisms 118 and 118.
The laser light 11 oscillated inside the laser chamber 2 is transmitted through the rear window 109, and passes through the rear opening 34 and the two prisms 118 and 118. Subsequently, it is reflected at the rear mirror 106, passes through the dispersion prisms 118 and 118 and the rear opening 34 once again, and is transmitted through the rear window 109 to return to the laser chamber 2. The laser light 11 passes through the front window 107 and the front opening 33, and is partly transmitted through the front mirror 8 to be emitted forward.
In this situation, in the laser light 11 oscillated inside the laser chamber 2, high-power intense line light 11A (wavelength 157.6299 nm) and low-power weak line light 11B (wavelength 157.5233 nm) coexist. Since the intense line light 11A and the weak line light 11B have different wavelengths, refraction angles at which they enter and exit the dispersion prisms 118 and 118 differ from each other. As a result, while the intense line light 11A and the weak line light 11B are passing through the two dispersion prisms 118 and 118, optical paths thereof deviate from each other little by little.
The intense line light 11A passes through the rear opening 34 and the front opening 33 and is emitted from the front mirror 8. On the other hand, the weak line light 11B has its optical path deviated while it goes and returns through the two dispersion prisms 118 and 118 and is blocked by either the rear slit 117 or the front slit 116, and as a result it is not oscillated. Thus, only the intense line light 11A is oscillated, thereby narrowing the bandwidth of the wavelength of the laser light 11.
However, the application of the band narrowing means with use of the above dispersion prisms 118 and 118 to the fluorine laser device 1 has the following disadvantages.
Specifically, during discharge to excite the laser medium, a spontaneous emission occurs in every direction from the excited fluorine from the fluorine laser device 1. Of the above spontaneous emissions, those traveling in the same direction as the laser light 11 interact with a number of excited molecules and inductively emit a large quantity of photon. It is known that the spontaneous emissions traveling on approximately the same axis of the laser light 11 are intensified as a result of the above. The intensified spontaneous emission is called an amplified spontaneous emission 36 hereinafter.
As shown in FIG. 21, the amplified spontaneous emission 36, for example, emitted rearward from the laser chamber 2 is hit against the slits 116 and 117 to be reflected since it has a larger broadening angle than the laser light 11. In this situation, it sometimes happens that the amplified spontaneous emission 36 which is hit against the slits 116 and 117 is irregularly reflected and returns into the laser chamber 2. As a result, part of discharge energy for amplifying the laser light 11 is spent to amplify the amplified spontaneous emission 36 once again, thus causing the disadvantage of reducing the power of the laser light 11.
Further, it sometimes happens that the weak line light 11B is irregularly reflected at the slit 16 and returns into the laser chamber 2 as the amplified spontaneous emission 36, and is amplified again by discharge in the laser chamber 2. Thus, the intense line light 11A and the weak line light 11B are mixed in the emitted laser light 11 to reduce the monochromatic property of the laser light 11 and the spectral width of the wavelength is increased. As a result, for example, when the laser light 11 is used for laser machining, there arises the disadvantage of machining accuracy being reduced.
The present invention is made to eliminate the above disadvantages of the prior art, and its object is to provide a fluorine laser device capable of obtaining high-power laser light with large monochromatic property.
In order to attain the above object, a first configuration of a fluorine laser device according to the present invention is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light,
a front slit disposed in front of the laser chamber and having a front opening for transmitting the laser light, and
a rear slit disposed behind the laser chamber and having a rear opening for transmitting the laser light,
at least one of the front slit and the rear slit is a slit in which a slit inclined plane is formed on a surface at a laser chamber side to make one of the front opening and the rear opening convex.
According to the above configuration, amplified spontaneous emission generated inside the laser chamber hits against the slit inclined plane and is reflected in a direction away from the laser chamber, and thus less of it returns into the laser chamber. Accordingly, less of the amplified spontaneous emission is amplified, and the ratio of energy spent for oscillation of the laser light increases, thus increasing the power of the laser light.
Further, in the fluorine laser device, the slit with the slit inclined plane being formed may further have a slit inclined plane formed on a surface at an opposite side to the laser chamber to make one of the front opening and the rear opening convex.
According to the above configuration, weak line light, which is reflected, for example, at the rear mirror and the front mirror and returns in the direction of the laser chamber, hits against the slit inclined plane and is reflected in the direction away from the laser chamber. As a result, less of the weak line light returns into the laser chamber to be amplified again, and only intense line light is amplified and oscillated. Accordingly, the monochromatic property of the laser light is improved, and for example, when the laser light is used for laser machining, machining accuracy is improved. Further, the amplified spontaneous emission reflected, for example, at the rear mirror and the front mirror also hits against the slit inclined plane and is reflected in the direction away from the laser chamber, and thus less of it returns into the laser chamber.
Further, in the fluorine laser device, the slit with the slit inclined plane being formed has black nickel plating applied onto a surface at the laser chamber side.
According to the above configuration, the amplified spontaneous emission and the weak line light generated inside the laser chamber are absorbed by the black nickel plating, and less of them is irregularly reflected and returns into the laser chamber.
A second configuration of the fluorine laser device is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light,
a front slit disposed in front of the laser chamber and having a front opening for transmitting the laser light, and
a rear slit disposed behind the laser chamber and having a rear opening for transmitting the laser light,
at least one of the front slit and the rear slit is a slit in which black nickel plating is applied onto a surface at a laser chamber side.
According to the above configuration, the amplified spontaneous emission and the weak line light generated inside the laser chamber are absorbed by the black nickel plating. The amplified spontaneous emission and the weak line light which are not absorbed by the black nickel plating hit against the slit inclined plane and are reflected in the direction away from the laser chamber, and thus further less of them returns into the laser chamber.
A third aspect of a fluorine laser device according to the present invention is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light, and
a rear mirror disposed behind said laser chamber and reflecting the laser light,
the rear mirror is a rear mirror in which a rear mirror total reflection portion for reflecting the laser light at high reflectivity is formed only at a portion to which the laser light is emitted.
According to the above configuration, the laser light is reflected at the rear mirror total reflection portion at high reflectivity and returns into the laser chamber and is amplified. On the other hand, since the amplified spontaneous emission generated in the laser chamber has a larger broadening angle than the laser light, it hits against the portion other than the rear mirror total reflection portion and is, for example, absorbed or reflected in the direction away from the laser chamber. Accordingly, less of the amplified spontaneous emission returns into the laser chamber.
Further in the fluorine laser device, the rear mirror with the rear mirror total reflection portion being formed may have a rear mirror inclined plane formed at an outer perimeter of the rear mirror total reflection portion to make the rear mirror total reflection portion convex.
According to the above configuration, since the amplified spontaneous emission has a larger broadening angle than the laser light, it hits against the rear mirror inclined plane and is reflected in the direction away from the laser chamber. Accordingly, less of the amplified spontaneous emission returns into the laser chamber.
A fourth configuration of a fluorine laser device according to the present invention is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light, and
dispersion prisms disposed behind the laser chamber and refracting the laser light,
the dispersion prisms have prism transmission portions for transmitting the laser light and prism inclined planes formed at outer perimeters of the prism transmission portions to make the prism transmission portions convex.
According to the above configuration, the laser light is transmitted through the prism transmission portions. On the other hand, since the amplified spontaneous emission generated in the laser chamber has a larger broadening angle than the laser light, it hits against the prism inclined planes at the opposite chamber side of the prism transmission portions and is reflected in the direction away from the laser chamber. Accordingly, less of the amplified spontaneous emission returns into the laser chamber.
A fifth configuration of a fluorine laser device according to the present invention is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light, and
a front window and a rear window respectively disposed at a front and a rear portion of the laser chamber and transmitting the laser light,
at least one of the front window and the rear window has a window transmission portion for transmitting the laser light and a window inclined plane formed at an outer perimeter of the window transmission portion to make the window transmission portion convex, on a surface at an opposite side to the laser chamber.
According to the above configuration, the amplified spontaneous emission generated in the laser chamber is reflected at the front mirror and returns in the direction of the laser chamber, and thereafter it hits against the window inclined plane and is reflected in the direction away from the laser chamber. Accordingly, less of the amplified spontaneous emission returns into the laser chamber.